Discussion in "ARM Development" started by    shyam    Dec 23, 2007.
Sun Dec 23 2007, 05:36 AM
consider the following example replace wait() with any delay routine....

int main (void)  
  unsigned int j;                /* LED var */

  IODIR1 = 0xFF0000;    /* P1.16..23 defined as Outputs */


 while (1)  
{                                      /* Loop forever */
    for (j = 0x010000; j < 0x800000; j <<= 1) { /* Blink LED 0,1,2,3,4,5,6 */
      IOSET1 = j;                                                   /* Turn on LED */
      wait ();                                                          /* call wait function */
      IOCLR1 = j;                                                  /* Turn off LED */
    for (j = 0x800000; j >
 0x010000; j >
=1 ) { /* Blink LED 7,6,5,4,3,2,1 */
      IOSET1 = j;                                                    /* Turn on LED */
      wait ();                                                           /* call wait function */
      IOCLR1 = j;                                                   /* Turn off LED */

this is a very simple code but tells the main differences between 51 and arm.....

[ Edited Sun Dec 23 2007, 05:49 AM ]
Sun Dec 23 2007, 05:41 AM

Important for reading:
just download lpc2148 usermanual user.manual.lpc2141.lpc2142.lpc2144.lpc2146.lpc2148.pdf

x can be 0 1 ur choice of port

GPIO Port Output Set register. This register
controls the state of output pins in
conjunction with the IOCLR register. Writing
ones produces highs at the corresponding
port pins. Writing zeroes has no effect.

IOCLR GPIO Port Output Clear register. This
register controls the state of output pins.
Writing ones produces lows at the
corresponding port pins and clears the
corresponding bits in the IOSET register.
Writing zeroes has no effect.

IOSET n IOCLR are both 32 bit registers....

the above code snippet says value of j will be sent to IOSET now in the IOSET register wherever there is a 1 there will be a high on the corresponding bit of the corresponding port...

IOSET1 =0x01 => P1.0 is high
IOSET1 = 0x02 => P1.1 high
IOSET1 = 0x03 => P1.0 and P1.1 are high
IOSET1 = 0x80000000 => P1.31 high ...........

important point.......

suppose the following sequence

IOSET1 =0x00;

what is the output??

P1.1 is still high because Writing zeroes has no effect.


all this while we have been trying to use IOs as output pins......

but we require them as inputs too.....

this is where IOPIN comes in

IOPIN ==> GPIO Port Pin value register. The current
state of the GPIO configured port pins can
always be read from this register, regardless
of pin direction.

thus consider the sequence....
IOSET1 = 0x0F;
IOCLR1 = 0x02;
Int_Buffer = IOPIN1;

value of Int_Buffer = 0x0D...

imp note =>

=> P1.0 - P1.7 has been configured as output pins......
we can not take input at these input...

thus look again at the above stated sequence...

now if i have a press-2-on switch on pin P1.0... can i read the status????


the IOPIN1 will still return 0x0D..

there fore the IODIR1 shud be written
IODIR1 = 0xFE;

Points to remember.....

  1. status of port pins can only be read thru IOPIN register.....
  2. IODIR has a default value of 0x00 so by default port pins are configured as input.
  3. change in IOSET register has no effect on IOCLR and vice versa..
  4. IODIR IOSET IOCLR IOPIN are all individual 32 bit registers..
  5. a pin once configured as output can not be used as input unless the value of corresponding IODIR register is changed.
  6. ports in LPC/arm are not bit addressable!!

this is all about writing to a pin and reading from pins

next we will discuss the PINSEL register....

[ Edited Sun Dec 23 2007, 05:51 AM ]
Fri Dec 28 2007, 02:00 PM
further discussion will be over here..
 Technophile like this.

Get Social


Powered by e107 Forum System


Wed May 20 2020, 03:59 AM
Does anyone have microcontroller programming software for STC15F104W (core 8051, 4 k, 128 byte, 6 I/O pin, UART ... DIL8), that works?
Sun May 03 2020, 01:08 AM
Tamu Gurung
Hi I am looking for a assembly language program for a digital decimal counter. Time counts max limit of 2 mins starting from 2.00 mins and ending at 0.00. time is to be displayed on 4 7-segment LED displays. Edsim51 simulator to be used. Thanks
Wed Mar 25 2020, 07:09 PM
Sir kindly send the code file i2c for 8051
Sat Mar 14 2020, 04:06 AM
@ Rohitnani,ABEBE..which project ?
Fri Mar 13 2020, 06:25 PM
how can get hadwere of this project
Sat Mar 07 2020, 09:41 PM
Sir, Could you please send me the zip file input password....
Wed Feb 26 2020, 09:28 PM
Peter Parker
Is it possible to send multiple messages using only 1 GSM module?
Sat Feb 01 2020, 02:42 PM
Pearl Olin
Wed Jan 22 2020, 10:46 PM
I m getting errors while simulation process during interfacing socket output and lcd... Can i get the report of ur project which is same as us.
Tue Jan 14 2020, 11:38 AM
shubham kharade
when i am trying to simulate the program in Proteus 8 professional, I am getting some errors as cannot find module file dhtxx.md can u help me



Thu May 21 2020, 08:44 AM
Wed May 20 2020, 09:28 PM
Wed May 20 2020, 03:05 PM
Wed May 20 2020, 07:52 AM
Wed May 20 2020, 03:15 AM
Tue May 19 2020, 06:08 PM
Tue May 19 2020, 02:22 PM
Mon May 18 2020, 09:50 PM


Guests: 53, Members: 0 ...

most ever online: 182184
(Members: , Guests: 182184) on 06 Aug 2010: 01:37 AM

Members: 38211
Newest member: Davidthils
Forum Activity
xrxx Avatar
Posted By xrxx
Thu Apr 30 2020, 06:59 AM
BCD MULTIPLICATIONAssume that you have to 2 BCD nu...
liqian Avatar
Posted By liqian
Tue Apr 28 2020, 05:26 AM
I happened to see your post and I got many useful ...
ExperimenterUK Avatar
Posted By ExperimenterUK
Tue Apr 28 2020, 04:21 AM
The code is hard to read.Please zip it and attach ...
rogermado Avatar
Posted By rogermado
Sun Apr 26 2020, 01:53 AM
@ExperimenterUK, thanks for your reply. You'll fin...
ExperimenterUK Avatar
Posted By ExperimenterUK
Sat Apr 25 2020, 05:42 PM
Some simulators handle displays better than others...
rogermado Avatar
Posted By rogermado
Sat Apr 25 2020, 03:59 PM
Hello everyone, sorry in advance if i'm not in the...
PHANTOM28 Avatar
Posted By PHANTOM28
Fri Feb 28 2020, 10:25 AM
Hi.I hope you all can help me. I am relatively ne...
ExperimenterUK Avatar
Posted By ExperimenterUK
Fri Feb 21 2020, 05:05 PM
ajay_bhargav Avatar
Posted By ajay_bhargav
Fri Feb 21 2020, 04:45 AM
Yes you can do that.1. Create a channel @Thingspea...
ananyagupta Avatar
Posted By ananyagupta
Thu Feb 20 2020, 03:58 AM
With regards to the particular characters sent to ...